Light emitting diodes (LED) have attracted attention as light emitting elements with low power consumption. An insulating substrate is used in the mounting of such a light emitting element, and a metal layer that serves as circuitry (wiring) is provided on this substrate.
In such a configuration, the heat during light output of the LED affects the performance and the reliability of the light emitting element. As such, while resin can be used for the substrate in the case of low-output LEDs, in recent years, demand has grown for even higher levels of brightness. Accordingly, an alumina sintered compact is used as the substrate in the case of medium-output LEDs and a ceramic such as aluminum nitride or the like is used as the substrate in the case of high-output LEDs.
Additionally, there is a demand for improved light emission efficiency in light emitting devices constituted by mounting a light emitting element on the substrate with the configuration described above. As such, the metal layer provided on the substrate is covered with a resin of a whitish color (see Patent Literature 1).